Stand-alone heating appliances are typically used as either sources of heat and/or for primarily decorative or aesthetic purposes. They are most commonly comprised of natural gas or propane burning fireplaces or stoves, or wood or coal burning fireplaces or stoves. Such appliances present the ability for localized heating, as well as the often desirable ambiance of a burning flame. A significant percentage of modern day fireplaces and stoves that are installed are of the direct vent type, wherein the firebox is sealed from the room within which the appliance is installed and combustion air is drawn from an outside environment. Direct vent fireplaces and stoves typically include at least one transparent (or largely transparent) external pane or surface (typically a front and/or end surface) to permit viewing of the interior of the firebox. These transparent panes or surfaces not only assist in sealing the firebox to allow for the proper functioning of a direct vent appliance, but also serve as a safety barrier preventing contact with the interior of the firebox. In the case of a natural vented fireplace or stove (sometimes referred to as “B-vent” appliances) there may at times be installed on one or more sides of the appliance a transparent pane to help prevent contact with the interior of the firebox. In some cases, a wire mesh or screen may be utilized, while in still other instances a combination of a transparent pane and a wire mesh or screen may be employed to achieve a particular desired visual effect. Non-vented appliances may also have incorporated into one or more of their sides a transparent pane and/or a screen.
Regardless of the nature of the appliance at hand, the presence of a transparent pane, a screen, or a combination of a transparent pane and a screen on one or more exposed sides or surfaces of the appliance can fulfill both functional and aesthetic requirements. At the same time, such structures can present a potential safety hazard. When heat generating appliances are in operation, such transparent panes or screens can become heated to a degree significant enough to cause burns should an individual, pet, or object come into contact with them. In some jurisdictions regulations have been passed limiting the temperature to which these components can be heated during operation of the appliance.
In an attempt to help regulate the heating of exposed components or surfaces of a fireplace, stove or other such appliance, others have proposed the use of multiple panes of transparent material, offset by airspaces to provide a degree of thermal insulation. In addition, it has been suggested to direct air from an electric fan over exposed surfaces for a cooling effect. While such approaches have been somewhat successful in helping to limit the temperature of transparent panes or screens on the sides of the appliance, at times they can result in increased installation, manufacturing, and/or operating costs. Where existing solutions rely upon an electrically driven motor to operate a cooling fan, they not only impact manufacturing, installation and operating costs, but lose their effectiveness in the case of a power outage.